As a means of relating the structure of proteins to their function we are studying the enzyme, formyltetrahydrofolate synthetase, in detail. During the period of this award we plan to examine interactions between the substrates and enzyme using NMR techniques. We will take advantage of the fact that the paramagnetic ion Mn(II) is a component of the various enzyme-substrate complexes. Using the theory of relaxation enhancement by paramagnetic species we can measure the distance from the nucleus being examined and Mn(II). Moreover the effects of other substrates on this distance can be studied. We also plan to study the cation-induced reassociation of monomers to form catalytically active tetramer. We shall examine the effects of solution variables on this process in an attempt to gain better insight into this reaction.